The present invention relates to wheelchairs, and particularly to wheelchairs capable of moving the seat and back for tilting and reclining.
Wheelchairs often have a fixed seat consisting of a seating surface and a back frame. The seating surface is usually either horizontal or slightly tilted back, with the front edge of the seating surface slightly higher than the rear edge of that surface. If the wheelchair user sits in the same position in a wheelchair for a long period of time, pressure is continuously applied to the tissue on the portion of the user""s body (buttocks, legs, and/or back) that is bearing the user""s weight in that position. Blood circulation to that tissue will be reduced, and ulcers or other problems can result.
To avoid these problems, it is necessary for people sitting in wheelchairs to shift their body weight from time to time. This is often accomplished by tilting the seat portion of the wheelchair backwards so that the user""s weight is shifted away from the pressure points on the user""s body. Also, the user""s weight can be shifted by reclining the back frame.
A problem with wheelchairs that have both a tilt and recline capability is that the user""s body is subject to shear problems during the maneuvering of the tilt and the recline apparatus. Due to the displacement between the anatomical pivot of the hip and the seat/back pivot, shear forces are introduced in the recline process. Previous efforts to mitigate this shear force have resulted in only crude approximations of the correct location of the back. Another problem seen in existing recline chairs is a tendency of the individual to slide out of the seat after repeated reclines. This can be due to the shear forces. Also the way the hip rotates during the recline process can be different from how it rotates when the individual comes back up or unreclines.
It would be advantageous if there could be developed a wheelchair having a tilt apparatus and a recline apparatus, where the tilt and recline functions are operated to minimize the shear forces transmitted to the wheelchair user. Also, it would be advantageous if there could be developed a method of unreclining, i.e., returning the reclined backrest of a wheelchair to an upright position, without causing the wheelchair user to have a tendency to slide forward along the wheelchair seat. Further, there is a need for improvements in wheelchairs to make them more conformable to the user""s needs.
The above objects as well as other objects not specifically enumerated are achieved by a method of operating a wheelchair during an un-recline process where the wheelchair includes a seat frame and a back frame. The method includes positioning the wheelchair user in the wheelchair with the back frame reclined, and rotating the seat frame of the wheelchair so that the seat frame and the back frame form an angle that is within the range of from about 80 degrees to about 120 degrees. The back frame is unreclined by rotating the back frame and the seat frame while maintaining the angle between the seat frame and the back frame within the range of from about 80 degrees to about 120 degrees.
According to this invention there is also provided a method of operating a wheelchair during an un-recline process, where the wheelchair including a seat frame and a back frame. The method comprises positioning the wheelchair user in the wheelchair with the back frame reclined, and rotating the seat frame of the wheelchair and the back frame simultaneously so that the seat frame and the back frame form an angle that is within the range of from about 80 degrees to about 120 degrees. The back frame is unreclined by rotating the back frame and the seat frame while maintaining the angle between the seat frame and the back frame within the range of from about 80 degrees to about 120 degrees.
According to this invention there is also provided a method of operating a wheelchair during an un-recline process, where the wheelchair includes a seat frame and a back frame. The method includes positioning the wheelchair user in the wheelchair with the back frame reclined and the back frame at an initial position. The seat frame of the wheelchair is rotated at least about 20 from the initial position. Then the back frame is rotated so that the seat frame and the back frame form an angle that is within the range of from about 80 degrees to about 120 degrees. The back frame is then unreclined by rotating the back frame and the seat frame while maintaining the angle between the seat frame and the back frame within the range of from about 80 degrees to about 120 degrees.
According to this invention there is also provided a method of providing user conforming characteristics in a wheelchair comprising providing a wheelchair having at least two movable frame members that are movable with respect to an initial position. The wheelchair is programmed by positioning a wheelchair user in the wheelchair and moving a first one of the at least two movable frame members through a sequence of movement from the first movable frame member""s initial position to subsequent positions. The position of a second one of the at least two movable frame members is adjusted to conform the second movable frame member to the user in response to the movement of the first movable frame member. The amount of adjustment of the second movable frame member during the sequence of movement of first movable frame member is measured, and the measured amounts of adjustment are stored. The wheelchair is operated by automatically adjusting the position of the second movable frame member in response to movement of the first movable frame member and in accordance to the measured amounts of adjustment, thereby providing user conforming characteristics in the wheelchair.
According to this invention there is also provided a method of providing shear reducing characteristics in a wheelchair. The method includes providing a wheelchair having a back frame and a shear plate, the shear plate being movable with respect to the back frame, and the back frame being mounted for reclining at various angles of recline with respect to an initial position. The wheelchair is programmed by positioning a wheelchair user in the wheelchair and reclining the back frame from the initial position through a recline sequence of several different angles of recline. The shear plate is adjusted with respect to the back frame at each of the several different angles of recline to minimize the shear experienced by the user at each of the several different angles of recline. The amount of adjustment of the shear plate at each of the several angles of recline is measured. The wheelchair is operated by automatically adjusting the shear plate with respect to the back frame as the wheelchair back frame is reclined, thereby providing shear reducing characteristics in the wheelchair.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.